Hardware - PGS Computing

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7 Νοε 2013 (πριν από 4 χρόνια και 1 μήνα)

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HARDWARE

Chapter 16


A computer is an

information

processing machine


I
t can only follow

the instructions
it is given

What is a Computer?

I’m ONLY a

machine!

What is Hardware?


Hardware refers to all the parts of the
Computer we can touch.


A Basic Computer has 5 Hardware devices:



Monitor


Mouse


Keyboard


Printer


System Unit

What is Software?


Software refers to all the
programs

and
data that we use with the computer.


Examples


Appleworks


Microsoft Office


A program is a set of
instructions

which
tell the CPU what to do

Things a

computer must have
:

1)
A P
rocessor


The brain of the computer

2)
A M
emory


To remember the
programs

and
data

that it uses

3)

Input
device
s



To enter

information into the computer

4)
Output

device
s



To show us what it has done to our information

5)
Backing

storage

Devices


To save our information




Information

we input is stored as
Data



Information

has a meaning to us (
We understand it
)


Telephone Number: 0141 876 7654


Car Licence Plate: H789 IOS


Date of Birth: 24 05 87



Data

has no meaning to us (
made up of symbols
)


01417761652


H789IOS


240586

Data and Information

Input


Process


Output

INPUT

PROCESS

OUTPUT

Data is
INPUT

into the computer (
Input device
)

Data is
PROCESSED

to produce useful information (
CPU
)

Information is then
OUTPUT

(
Output device
)

More Input


Process


Output


This raw material is processed.


When the processing is completed a
useful thing is produced


Data is the
RAW MATERIAL

Input


Process


Output

INPUT

DEVICES

CENTRAL

PROCESSING

UNIT (CPU)

OUTPUT

DEVICES

BACKING

STORAGE

DEVICES

MAIN

MEMORY

Main Memory


The
Main Memory
is responsible for storing
the parts of a
program(s)
and

data
which are
in current use.



It is
IMMEDIATE ACCESS STORE.

MAIN MEMORY

A picture of
Main Memory
is below:

STORAGE
LOCATIONS

MEMORY

ADDRESSES

0000 0000

0000 0001

0000 0010

0000 0011

0000 0100

0000 0101

0000 0110

0000 0111

0000 1000

0101 0101

1111 1111

0000 1111

0000 0000

0101 0101

1111 0000

0101 0101

0101 0101

1100 11 00


The computer stores each item in its memory in a
storage
location.



A single storage location can hold
one byte

(a character)



Each storage location has a unique
address

so that, once data
has been stored there, it can be found again later when it’s
needed



The amount of
memory

a computer has depends on the number
of storage locations

ADDRESSABILITY


Random Access Memory Chip


Read/Write memory


Stores programs and data temporarily


Contents are lost when computer is switched off



Read Only Memory Chip


Stores programs and data permanently


Contents are not lost when computer


is switched off


Stores the Operating System

Main Memory Chips

RAM

ROM


Made of a material called silicon


Held on a printed circuit board inside the computer


Made up of thousands of tiny components


Very small size and work very fast


Produced very cheaply

Micro Chips

Size of Computers


Palmtop Computer


A small computer that can be held in the palm of your hand


Laptop Computer


A small portable computer that you can rest on your lap


Desktop Computer


A computer which normally sit on a desk and runs off the
mains


Mainframe Computer


Very powerful computers able to process 1000’s of times
more information a second than a desktop

Smallest

Biggest


T
he largest type of computer.


Used in

large organisations



Banks, Police



Internet Service Provider’s


Hundreds of people may use it at the same time


Cost
-


millions of pounds.

Mainframe

Computer



Mainframe computers:



are very big in size


normally take up a whole room



are extremely fast in operation



have very large memories



have a wide range of software and hardware



need air conditioning because of the heat they

generate

Mainframe

Computer


Backing Storage is used to store our programs and data


We need Backing storage because our data is lost from
Main Memory when the computer is turned off


Capacity of Backing Storage


Quantity of data that can be held on backing storage medium


Floppy Disk


CD ROM


Each medium has a different capacity


Floppy Disk


1.44 Megabytes


USB Memory Stick

16 Mb up to 2 Gb

Backing Storage


Random (Direct) Access


Ability to locate data straight away, wherever it is
stored and open it up


Fast access to files



Sequential Access


Retrieving data in the order that it was stored


Slower access to files


Types of Access


Random (Direct) Access



Floppy Disk Drive



Hard Disk Drive



CD
-
ROM Drive



Sequential Access



Tape Drive

Access Devices